1. Field of the Invention
The present invention pertains to wireless telecommunications, and particularly to the handling of headers for Internet-transmissible packets in a radio access network having varied header handling capability.
2. Related Art and Other Considerations
In a typical cellular radio system, mobile stations (MSs) communicate via a radio access network (RAN) to one or more core networks. The mobile stations can be mobile terminals such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the mobile stations within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a base station controller (BSC) which supervises and coordinates various activities of the plural base stations connected thereto.
Two examples of a radio access network is Global System for Mobile communications (GSM) developed in Europe and its third generation evolution GSM/EDGE Radio Access Netowrk (GERAN). Another example radio access network (which is also an evolution of GSM) is the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN). UTRAN of UMTS is essentially a wideband code division multiple access (W-CDMA) system.
According to the basic architecture for the third generation radio access networks (RANs) is a master/slave relationship between the RAN and the mobile station. The mobile station is able to indicate its capabilities to the RAN. Based on the service that is requested by the mobile station (MS) and the capabilities of the mobile station (MS), the RAN makes a configuration choice and signals this configuration to the mobile station (MS) over the radio interface using radio resource control (RRC) signaling. The configuration must then be supported by the mobile station (MS). If the MS cannot support the configuration, a failure must be sent.
Some radio access networks, particularly including the GERAN (GSM/EDGE Radio Access Network), accommodate both circuit switched and packet switched connections. Many types of packet switched connections, including some of those which provide speech service, utilize internet protocol (IP).
A significant challenge in running a service based on internet protocol (IP) is the considerably large overhead (e.g., aggregate headers) of a packet in relation to the payload. FIG. 7A illustrates an example generalized internet protocol (IP) packet; FIG. 7B illustrates an example internet protocol (IP) packet for speech comprising a RTP/UDP/IP header and speech payload. The RTP/UDP/IP header header of FIG. 7B typically begins with either an IPv4 or IPv6 field (twenty or forty octets, respectively), and also includes a UDP field (eight octets), and an RTP header (twelve octets). In either the IPv4 or IPv6 scenario, the RTP/UDP/IP header has a greater length than the thirty-two octet speech payload of the internet protocol (IP) packet. Regarding RTP and UDP in general, see RTP: A Transport Protocol for Real-Time Applications, RFC 1889; and J. Postel, User Diagram Protocol, RFC 761, September 1980, both of which are incorporated herein in their entirety.
Because of the large inefficiency illustrated by FIG. 7A and FIG. 7B, various header compression (HC) schemes have been developed to ensure that the impact of the overhead (e.g., RTP/UDP/IP header size) on the efficiency spectrum is reduced. Various examples of header compression are found in the literature and certain industry specifications and standards, examples of which are listed below.
The internet engineering task force (IETF) is the standardization body which carries out development and standardization for protocols to be employed in the internet. The following header adaptation protocols have been specified in the IETF (all of which are incorporated herein by reference in their entirety):                S. Casner, V. Jacobson, “Compressing IP/UDP/RTP Headers for Low-Speed Serial Links”, RFC 2508, February 1999.        Mikael Degermark, Bjorn Nordgren, Stephen Pink, “IP Header Compression”, RFC 2507, February 1999.        M. Engan, S. Casner, C. Bormann, “IP Header Compression over PPP”, RFC 2509, February 1999.        V. Jacobson, “Compressing TCP/IP Headers for Low-Speed Serial Links”, RFC 1144, February 1990.        RFC 3095 Robust Header Compression (ROHC): Framework and Four Profiles: RTP, UDP, ESP, and Uncompressed.        RFC 3096 Requirements For Robust IP/UDP/RTP Header Compression.        
For GERAN (GSM/EDGE Radio Access Network), an optimized voice bearer is currently being standardized which would provide a spectrum efficient way of transporting voice internet protocol packets originating in the Iu Interface (between the UTRAN and a core network) This spectrum efficiency is achieved by reusing the codec-specific channel coding from GSM over the air interface. To conform to the payload format of this channel coding, a procedure know as header removal (HR) is performed to remove the RTP/UDP/IP header before transporting the packets over the air interface. The RTP/IUDP/IP header may then generated after the air-interface. The standardization of the header removal algorithm to be employed by GERAN is under the responsibility of the Technical Specification Group GSM/EDGE Radio Access Network (TSG GERAN) group within the 3rd Generation Partnership Project (3GPP).
There are, however, other types of speech service potentially available in GERAN (GSM/EDGE Radio Access Network). For example, a general multimedia (MM) bearer with true multimedia (MM) capabilities and transparent IP connectivity is envisioned. See, e.g., 3GPP TS 23.228, V5.0.0 (2001-04), 3rd Generation Partnership Project: Technical Specification Group Services and System Aspects; IP Multimedia (IM) Subsystem—Stage 2 (Release 5); and 3GPP TS 23.002, V5.0.0 (2000-12), 3rd Generation Partnership Project: Technical Specification Group Services and System Aspects; Network Architecture (Release 5). This general IP multimedia (MM) bearer is to provide transparent IP connectivity and enable sessions where speech is but one of the possible media types (other possible media types are video, shared white-board, streaming, etc.). Transparency in this context means that the IP headers arrive unchanged at the end terminal (this cannot be guaranteed by the header removal scheme employed on the optimized voice bearer). Transparency is a prerequisite for providing synchronization between different media. The multimedia (MM) bearer can utilize header compression (such as one of the compression techniques discussed above), or alternatively have no header adaptation mechanism in order to facilitate this transparency.
While GERAN supports header compression protocols such as various ones listed above, the strategy proposed for optimized speech in GERAN to date involves utilization of header removal for the reasons above mentioned. Header removal strips the internet protocol (IP) headers and transmits only the payload. However, at least initially in header removal, state information may be exchanged between peer entities to ensure that regeneration of the internet protocol (IP) headers is possible.
The above-mentioned Iu Interface is an open standardized interface that can be used for many different radio access networks (RANs). Currently, the Iu Interface is used for the UMTS Terrestrial RAN (UTRAN), as described (for example) in 3GPP TS 25.413. The Iu Interface can now also be used for GERAN (GSM/EDGE Radio Access Network). Since the Iu Interface is an open interface, it would extremely undesirable to modify the set of possible radio access bearer (RAB) attributes and value ranges involved with the Iu Interface for the purpose of configuring GERAN specific parameters. In fact, modifying the possible radio access bearer (RAB) attributes and value ranges would change the existing quality of service concept for all radio access networks that use the Iu Interface.
What is needed, therefore, and an object of the present invention, is a technique for correctly configuring radio bearers for appropriate RTP/UDP/IP header optimization or adaptation schemes in an efficient way within existing network architectural concepts.